1. Field of the Invention
This invention relates to the field of variable friction ring gearing.
2. Background of the Invention
German Patent No. 21 26 122 describes an annular friction gear comprising an outer conical disc connected to a driving shaft and an outer conical disc connected to a driven shaft, the axes of the discs being mutually offset. Power is transmitted between the discs by a ball bearing. The inner race of the bearing is in the form of a friction element having two inner conical chamfers contacting outer conical discs. One side of the inner race rests on one disc, the other size of the inner race rests on the other conical disc. When the ball bearing is displaced radially along the line connecting the inner conical chamfers of the inner race, one running diameter on one disc is displaced toward the center and the other running diameter on the other disc is displaced by the same amount away from the center.
An annular friction gear of this type requires an offset between the driving shaft and driven shaft. Also, the form of the conical discs and the shape of the inner race of the bearing cause its individual parts to be relatively complicated and expensive to manufacture.
German Patent No. 812,618 describes an annular friction gear in which driving and driven shafts and associated flat discs are arranged coaxially. To transmit power, a radially displaceable friction element comprising two friction rings is located between the driving disc and driven disc. Each friction ring has a conical friction surface and a hollow shaft formed integrally at the center of the side remote from the friction surface. A helical spring, located within hollow shafts surrounded by a sleeve, presses friction rings away from each other and against the flat surfaces of the driving disc and driven disc.
In the arrangement of this type, relatively large axial dimensions are required because of the design of the friction element in the axial direction. In addition, the friction element is constructed in a complicated manner and cannot be produced economically.